Therapeutic agent for virus-associated malignancy

ABSTRACT

A therapeutic agent comprising fucoxanthin or fucoxanthinol as an active component is disclosed. The therapeutic agent is effective and high clinical utility for medical treatment and prevention of virus-associated malignancy such as adult T-cell leukemia and Burkitt lymphoma.

TECHNICAL FIELD

The present invention relates to a therapeutic agent forvirus-associated malignancy and, more particularly, to a therapeuticagent for virus-associated malignancy effective for treating orpreventing malignancy caused by viral infection such as adult T-cellleukemia and Burkitt's lymphoma.

DESCRIPTION OF BACKGROUND ART

In the present specification, virus-associated malignancy indicates amalignancy caused by viral infection as an origin such as adult T-cellleukemia (hereinafter referred to as “ATL”) and Burkitt's lymphoma(hereinafter referred to as “BL”).

Among these, ATL is a poor-prognosis leukemia/limphoma originating froma CD4± T-lymph cell induced by infection with human T-cell leukemiavirus type-I (hereinafter referred to as “HTLV-I”), which is a humanretrovirus. The number of HTLV-I-infected persons (HTLV-I carriers) ispresumed to be about 1,200,000 in Japan (about 1% of the population).There is a local specificity to the number of HTLV-I carriers. In Japan,there are many HTLV-I carriers in the southwest district (Kyushu,Okinawa, and Shikoku). Worldwide, there are many HTLV-I carriers intropical areas such as the Caribbean area and South America.

Many leukemia cells originating from ATL have a phenotype of CD4positive and CD8 negative helper T-cells and are accompanied by uniquenuclear denaturing. HTLV-I which is a C-type retrovirus and was calledATLV at the beginning, has been identified to be a causative virus ofATL, and epidemiological investigations have revealed that HTLV-Icarriers have not only increased incidence of ATL, but also increasedincidence of malignancy in general, and that nervous system diseasecalled HAM (HTLV-I-associated myelopathy) and immunological diseases areinduced in HTLV-I carriers. In this manner, HTLV-I is revealed as beingrelated not only to ATL but also to other diseases.

Moreover, the involvement of HTLV-I in rheumatism-like chronicarthritis, Sjogren's syndrome, uveitis of the eyes, and the like hasbeen indicated. ATL induced by infection with HTLV-I rapidly becomesserious once developed and its medical treatment is extremely difficult.Chemotherapy or radiotherapy applicable to malignant lymphoma hasconventionally been used for treating ATL. However, they are a temporarysymptomatic treatment and not an essential treating method.

On the other hand, Burkitt lymphoma (BL) is a blood tumor of which oneof the causes is infection with Epstein-Barr virus (hereinafter referredto as “EBV”) which is a kind of herpesviruses. There are manyEBV-related BLs among opportunistic lymphoma induced in patients with animpaired immune system and such BLs also exhibit a poor-prognosis. EBVis also a causative virus inducing infectious mononucleosis among youngadults and is known to be related to nasopharyngeal carcinoma, somestomach cancers, and Hodgkin's disease.

However, there is no medicine having a high clinical efficiency and highsafety for treating these virus-associated malignancy caused by viralinfection. Development of a novel medicine has been strongly desired.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Therefore, an object of the present invention is to discover a substrateeffective for medical treatment and prevention of virus-associatedmalignancy and to develop a therapeutic agent for virus-associatedmalignancy with high clinical utility using the substrate.

MEANS FOR SOLVING THE PROBLEM

The present inventors have undertaken research on the subject of HTLV-1and EBV and investigated medicines clinically useful for treating ATLand BL for a long period of time. As a result, the present inventorshave found that fucoxanthin and fucoxanthinol contained in seaweeds actspecifically on virus-associated malignancy and can attain the objectiveof functioning as a curative medicine. This finding has led to thecompletion of the present invention.

Accordingly, the present invention provides a therapeutic agent forvirus-associated malignancy comprising fucoxanthin or fucoxanthinol asan active component.

In addition, the present invention provides a method of treatingvirus-associated malignancy comprising administering fucoxanthin orfucoxanthinol to a patient having virus-associated malignancy.

The present invention further provides use of fucoxanthin orfucoxanthinol in manufacture of a therapeutic agent for virus-associatedmalignancy.

EFFECT OF THE INVENTION

Fucoxanthin and fucoxanthinol, which are active components of thetherapeutic agent for virus-associated malignancy of the presentinvention (hereinafter referred to as “malignancy treating agent”),selectively act on HTLV-1-infected cells and ATL cells, butsubstantially do not act on normal cells. Specifically, theconcentration of fucoxanthin or fucoxanthinol causing apoptosis in thesecells is significantly lower than the corresponding concentration ofβ-carotene or astaxanthin. Especially, fucoxanthinol causes apoptosis ata concentration of one micromole or less and the survival rate of theabove-mentioned cells is almost zero.

Since fucoxanthin and fucoxanthinol cause apoptosis specifically invirus-associated malignancy at a significantly high rate, a malignancytreating agent containing fucoxanthin or fucoxanthinol as an activecomponent is very useful for treating or preventing malignancy generatedby viral infection such as ATL or BL.

BEST MODE FOR CARRYING OUT THE INVENTION

The active component of the malignancy treating agent of the presentinvention is fucoxanthin or fucoxanthinol. Among these, fucoxanthin is acompound contained in seaweeds which we take routinely, for example,brown algae such as Undaria pinnatifida, Laminaria, and Hedwigiaceae.Fucoxanthin is a carotenoid with low toxicity shown by the followingformula (I). Fucoxanthinol is a deacetylation compound obtained byhydrolysis of fucoxanthin and is shown by the following formula (II).

Fucoxanthin has been known to exhibit growth-suppressing activity ofneuroblastoma, prostatic cancer, malignant melanoma, colorectal cancer,and acute promyelocytic leukemia cells and to exhibit carcinogenicretardation activity for colorectal cancer and a duodenum tumor invitro. However, fucoxanthin is not known to exhibit outstandingantitumor activity against other cancers, for example, virus-associatedmalignancy such as virus-related leukemia and lymphoma. Furthermore,fucoxanthinol which is a deacetylation compound of fucoxanthin has notbeen known to exhibit a more excellent antitumor activity againstvirus-associated malignancy as compared with fucoxanthin.

Thus, the fact that fucoxanthin and fucoxanthinol can be effectivelyused as an agent against virus-associated malignancy for preventing andtreating ATL and BL has been discovered for the first time by thepresent inventors.

As mentioned above, fucoxanthin is a compound contained in brown algaesuch as Undaria pinnatifida, Laminaria, and Hedwigiaceae. As an exampleof fucoxanthin preferably used in the present invention, a refinedfucoxanthin product obtained by dipping brown algae such as seaweeds ofSargassum fulvellum or dry Underaia pinnatifida in an organic solventsuch as methanol or acetone for about 18 hours at room temperature undershaded conditions to obtain an extract, condensing the extract, andseparating fucoxanthin by liquid chromatography such as Diaion HP20™(manufactured by Mitsubishi Chemical Corp.), Toyopearl HW40F™(manufactured by Tosoh Corp.), or ODS (Wakogel 50C18™ manufactured byWako Pure Chemical Industries, Ltd.), and refining the fucoxanthin byrepeating recrystallization can be given.

Fucoxanthinol is a deacetylation compound obtained by hydrolysis offucoxanthin and can be obtained by, for example, reacting varioushydrolases with fucoxanthin.

More specifically, as an example of the fucoxanthinol used in thepresent invention, fucoxanthinol obtained by a method partly modifying alipase decomposition method described by T. Matsuno, M. Ookubo, T.Nishizawa, and I. Shimizu (Chem. Pharm. Bull., 32, 4309-4315 (1984)) canbe given.

The above-mentioned fucoxanthin or fucoxanthinol can be used as anactive component of the malignancy treating agent of the presentinvention after purifying by a known purification method, if necessary.

Specifically, in order to prepare the malignancy treating agent of thepresent invention, fucoxanthin or fucoxanthinol (hereinafter referred tofrom time to time as “fucoxanthins”) may be combined with known drugcarriers, as required.

The malignancy treating agent can be prepared into orally administeredforms such as tablets, capsules, a powder preparation, granules, aliquid preparation, and a syrup, or parenterally administered forms suchas an injection, an agent for an intravenous drip, a drug for externalapplication, a suppository, and a pasting agent.

As examples of the drug carrier which can be used for preparing thesepreparations, known carriers for solid preparations, including vehiclessuch as starch, lactose, sucrose, mannitol, corn starch,microcrystalline cellulose, carboxymethylcellulose, and silicic-acidsugar; binders such as polyvinyl alcohol, polyvinyl pyrrolidone,polyvinyl ether, ethyl cellulose, gum arabic, traganth, gelatin,hydroxypropyl cellulose, dextrin, and pectin; lubricants such asmagnesium stearate, talc, and polyethylene glycol; disintegrators;disintegrator adjutants; stabilizers; and carriers for liquidpreparations, including liquid components such as water, ethyl alcohol,ethylene glycol, and glycerol; surfactants such as polyoxyethylenesorbitan fatty acid ester; taste components such as glucose and aminoacid; solubilizing agents; colorants; and preservatives can be given.For forming preparations for external application, suppositories, andpasting agents, carriers known in the art conforming to respective formscan be used.

The amount of the fucoxanthins blended with the malignancy treatingagent of the present invention varies according to the type of thedisease, the degree of the disease, the age of the patient, and thelike. For example, in the case of an oral preparation in whichfucoxanthin is an active component, a preferable daily dosage for anadult is from about 0.1 mg to 300 mg, and about 1/10 of that amount inthe case of intravascular injection.

In the case of an oral preparation in which fucoxanthinol is an activecomponent, a preferable daily dosage for an adult is from about 0.05 mgto 100 mg, and about 1/10 of that amount in the case of intravascularinjection.

EXAMPLES

The present invention will be described in more detail by way ofReference Examples and Examples which should not be construed aslimiting the present invention.

Reference Example 1 (Preparation of Fucoxanthin)

3.15 kg of dry Sargassum fulvellum was cut into pieces and extractedtwice using 20 L of methanol at room temperature for 18 hours. Theextract was concentrated to 1 L and partitioned twice using 800 mL ofhexane each time. The methanol layer was concentrated. The concentratewas added to a HP20 column (φ55×150 mm) and eluted with 1.5 L ofmethanol and 600 mL of acetone. The fraction eluted with methanol wasconcentrated. The concentrate was added to a HW40F column (φ30×500 mm)and eluted with methanol. A fucoxanthin fraction was concentrated andthe concentrate was recrystallized from 90% methanol twice to obtain 200mg of purified fucoxanthin. The fucoxanthin purity was confirmed to be95% or more by HPLC and a ¹H-NMR spectrum and the chemical structure wasconfirmed by NMR and MS spectra. The resulting purified fucoxanthin wasused in the following Examples.

Reference Example 2 (Preparation of Fucoxanthinol)

100 mg of the purified fucoxanthin obtained by Reference Example 1 wasdissolved in 2 mL of acetone. On the other hand. 2 g of Candidarugosaorigin-lipase (manufactured by Sigma) was used as the lipase anddissolved in 22.5 mL of a 0.1 M phosphate buffer solution (pH 7.0). Bothsolutions were mixed and the mixture was heated at 37° C. for 18 hours.The reaction solution was filtered and the solvent was removed. Theresidue was extracted with 50 mL of acetone to collect a fucoxanthinreaction product. The reaction product was again subjected to the abovelipase reaction. The resulting fucoxanthin reaction product wasseparated and purified by HPLC (Cosmosil ODS 5C18-AR-II20×250 mm, 80%MeOH, 5 mL/min, manufactured by Nacalai Tesque, Inc.) to obtain purifiedfucoxanthinol. The fucoxanthinol purity was confirmed to be 95% or moreby HPLC and a ¹H-NMR spectrum and the chemical structure was confirmedby NMR and MS spectra. The resulting purified fucoxanthinol was used inthe following Examples.

Example 1 Measurement of Proliferation Potency of Viral-Infected CellStrains (Method)

Cells of HTLV-I-infected T-lymph cell lines (MT-2, MT-4, HUT-102.ED-40515 (−)) EBV-infected B cell lines (Raji. Daudi, B95-8/BJAB.B95-8/Ramos, LCL-Ka, LCL-Ku), a cervical cancer cell line (HeLa), and achronic myeloid leukemia cell line (K-562), each adjusted to aconcentration of 2×10⁵ cells/mL with an RPMI 1640 culture mediumcontaining 10% fetal bovine serum, were spread over a 96-well plate inan amount of 1×10⁴ cells/well.

Next, 50 μL/well of fucoxanthin, fucoxanthinol, β-carotene, andastaxanthin were added to make final concentrations of 10, 5, 2.5, 1.25,and 0.625 μM (fucoxanthin and fucoxanthinol) or 10, 5, and 2.5 μM(β-carotene and astaxanthin), followed by incubation at 37° C. for 24hours. After adding “WST-8” (manufactured by Wako Pure ChemicalIndustries, Ltd.) in an amount of 5 μL/well as a coloring substrate,cells were cultured for four hours at 37° C. After culturing, absorbanceat a wavelength of 450 nm was measured by a microplate reader todetermine the survival rate of the cells using the following formula.

Cell survival rate(%)=[1−(A−B)/A]×100  [Formula 1]

A: Absorbance without agent treatment

A: Absorbance with agent treatment

(Results)

The effects of fucoxanthin and fucoxanthinol on proliferation potency ofHTLV-I-infected T-lymph cell lines or EBV-infected B cell lines areshown in FIG. 1 and FIG. 2. As is clear from these Figures, fucoxanthinand fucoxanthinol concentration-dependently suppressed the growth of allthe HTLV-I-infected T-lymph cell lines and EBV-infected BL cell lines.In addition, the capability of fucoxanthinol to inhibit growth of thesecell lines was found to be significantly higher than that offucoxanthin.

On the other hand, the results of the similar experiment in which theeffects of β-carotene and astaxanthin on proliferation potency ofHTLV-I-infected T-lymph cell lines were investigated are shown in FIG.3. As can be seen from the results, other xanthines have only a slighteffect on the growth of HTLV-I-infected T-lymph cell lines, whereas thefucoxanthins have an excellent growth inhibiting capability.

Example 2 Measurement of Proliferation Potency of Peripheral BloodMononuclear Cells in Healthy Person and Adult T-Cell-Leukemia (ATL)Patients (Method)

First, the peripheral blood mononuclear cells (PBMC) were separated bythe Ficoll centrifugal specific gravity method. The cells were dilutedwith an RPMI 1640 culture medium containing 10% fetal bovine serum to2×10⁶ cells/mL and spread over a 96-well plate in an amount of 1×10⁵cells/well.

Next, 50 μL/well of fucoxanthin and fucoxanthinol were added to makefinal concentrations of 10, 5, 2.5, 1.25, and 0.625 μM (fucoxanthin) or2.5, 1.25 and 0.625 μM (fucoxanthinol), followed by incubation at 37° C.for 24 hours. After adding WST-8 in an amount of 5 μL/well, the cellswere cultured for four hours at 37° C. After culturing, absorbance at awavelength of 450 nm was measured by a microplate reader to determinethe survival rate of the cells using the above formula.

(Results)

The effects of fucoxanthin and fucoxanthinol on proliferation potency ofthe PBMC of a healthy person and five adult T-cell-leukemia (ATL)patients are shown in FIG. 4. As is clear from the figure, fucoxanthinand fucoxanthinol concentration-dependently suppressed the growth ofleukemia cells in the ATL patients, but exhibited no toxicity againstthe PBMC of the healthy person. The effect of fucoxanthinol on growthpotency was higher than that of fucoxanthin.

Example 3 Measurement of Cell-Cycle of HTLV-I-Infected Cell Lines(Method)

1×10⁶ cells of HTLV-I-infected cell lines (MT-2, MT-4, HUT-102, ED-40515(−)) were scattered over a cell culture plate, and 5 μM of fucoxanthinwas added, followed by incubation at 37° C. for 24 hours. After 24hours, the cells were collected and dyed with propidium iodide tomeasure the DNA content using a flow sight meter. The cell cycle of eachcell was judged by calculating the distribution of the cell group ofeach cell cycle from the result of the DNA content.

(Results)

The effect of fucoxanthin on the cell cycle of the HTLV-I-infected celllines is shown in FIG. 5.

As a result, the cell groups were found to have increased in the GIphase, confirming that fucoxanthin suspends the cell cycle of allHTLV-I-infected cell lines at the G1 phase.

Example 4 Measurement of Apoptosis HTLV-I-Infected Cell Lines (Method)

1×10⁶ cells of HTLV-I-infected cell lines (MT-2, MT-4, HUT-102, ED-40515(−)) were scattered over a cell culture plate, and fucoxanthin (10, 5,and 2.5 μM) or fucoxanthinol (10, 5.25, 1.25, and 0.625 μM) was added,followed by incubation at 37° C. for 24 hours. After 24 hours, the cellswere collected and dyed with annexin V to measure the rate (%) ofapoptosis-positive cells using a flow sight meter.

(Results)

The effect of fucoxanthinol on apoptosis of HTLV-I-infected cells isshown in FIG. 6 and the relationships between the concentration offucoxanthin and fucoxanthinol with the apoptosis of MT-2 are shown inFIGS. 7 and 8 respectively. It can be seen from the results thatfucoxanthin induces apoptosis in all HTLV-I infected cell lines (FIG. 6)and that the effect is concentration dependent (FIG. 7). It was alsoconfirmed that fucoxanthinol induces apoptosis in MT-2, one of theHTLV-I-infected cell lines, and that the effect is stronger than that offucoxanthin (FIG. 8).

INDUSTRIAL APPLICABILITY

As shown in the above Examples, fucoxanthin and fucoxanthinolconcentration-dependently reduce the survival rate of malignancy relatedto viruses such as HTLV-I-infection T-lymph cell lines, EBV-infected BLcell lines, EBV-infected B cell lines, and ATL cells, without affectingthe peripheral blood mononuclear leukocytes of healthy persons.

Therefore, the therapeutic agent for virus-associated malignancy of thepresent invention has a selective anti-tumor effect on viral infectedlymphocytes and can be used as a practically applicable novel agent fortreating or preventing ATL, Burkitt lymphoma, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows effects of fucoxanthin and fucoxanthinol on proliferationpotency of HTLV-I-infected T-lymph cell lines, wherein A shows theeffect of fucoxanthin and B shows the effect of fucoxanthinol.

FIG. 2 shows effects of fucoxanthin and fucoxanthinol on proliferationpotency of EBV-infected B cell lines, wherein A shows the effect offucoxanthin and B shows the effect of fucoxanthinol.

FIG. 3 shows effects of β-carotene and astaxanthin on proliferationpotency of HTLV-I-infected T-lymph cell lines, wherein A shows theeffect of β-carotene and B shows the effect of astaxanthin.

FIG. 4 shows effects of fucoxanthin and fucoxanthinol on the survivalrate of peripheral blood mononuclear leukocytes of healthy persons andATL patients, wherein A shows the effect of fucoxanthin and B shows theeffect of fucoxanthinol.

FIG. 5 shows the effect of fucoxanthin on the cell cycle ofHTLV-I-infected cell lines.

FIG. 6 shows the effect of fucoxanthin on the apoptosis ofHTLV-I-infected cell lines.

FIG. 7 shows the concentration-dependent effect of fucoxanthin on theapoptosis of MT-2, which is one of the HTLV-I-infected cell lines.

FIG. 8 shows the concentration-dependent effect of fucoxanthinol on theapoptosis of MT-2, which is one of the HTLV-I-infected cell lines.

1. A therapeutic agent for virus-associated malignancy comprisingfucoxanthin or fucoxanthinol as an active component.
 2. The therapeuticagent according to claim 1, for treating or preventing adult T-cellleukemia or Burkitt lymphoma.
 3. The therapeutic agent according toclaim 1, wherein the agent is a preparation to be orally administered.4. The therapeutic agent according to claim 1, wherein the agent is apreparation to be parenterally administered.
 5. The therapeutic agentaccording to claim 2, wherein the agent is a preparation to be orallyadministered.
 6. The therapeutic agent according to claim 2, wherein theagent is a preparation to be parenterally administered.
 7. A method oftreating virus-associated malignancy comprising administering thetherapeutic agent according to claim 1 to a patient of thevirus-associated malignancy.